System and methods for intracranial vessel access

ABSTRACT

The invention relates to systems and methods for intracranial vessel access. In particular, a system including a co-axial combination of a steerable variable thickness microwire operatively supporting a tapered larger bore support and larger bore distal access catheter is described. Methods of advancing the intracranial access system through the vasculature are also described.

FIELD OF THE INVENTION

The invention relates to systems and methods for intracranial vesselaccess. In particular, a system including a co-axial combination of asteerable variable thickness microwire operatively supporting a taperedlarger bore support and larger bore distal access catheter is described.Methods of advancing the intracranial access system through thevasculature are also described.

BACKGROUND OF THE INVENTION

Acute ischemic stroke (AIS) is caused by a sudden blockage to one of thelarge intracranial vessels in the brain by a blood clot that movesthrough the intracranial vessels and where it becomes lodged within anarrowing vessel thus cutting off blood flow to a portion of the brain.AIS is usually a devastating disease that unless quickly treated tore-establish blood flow to the brain can result in significantimpairment of a patient's brain function.

Importantly, recent studies including “Randomized Assessment of RapidEndovascular Treatment of Ischemic Stroke” published on Feb. 11, 2015,at NEJM.org, and “Stent-Retriever Thrombectomy after Intravenous t-PAvs. t-PA Alone in Stroke” published on Apr. 17, 2015, at NEJM.org, haveshown that patient outcome is significantly improved by removing theblood clot quickly and safely. The effect of these studies has been thatendovascular treatment of stroke is now the standard of care as endorsedby the American Heart Association/American Stroke Association (see “2015AHA/ASA Focused Update of the 2013 Guidelines for the Early Managementof Patients With Acute Ischemic Stroke Regarding EndovascularTreatment—A Guideline for Healthcare Professionals From the AmericanHeart Association/American Stroke Association;www.stroke.ahajournals.org: ((Stroke. 2015;46:000-000.).

Recanalization are procedures that are used to remove the blood clot byguiding recanalization equipment through the blood vessels of the brainunder x-ray guidance. In a recanalization procedure, access to thevascular system is typically obtained in the patient's groin region byentering the common femoral artery and advancing a steerable wire withina coaxial balloon guide catheter through the vascular system to accessthe carotid artery. Often there may be a diagnostic preshaped catheterwith the balloon guide catheter to allow access to the relevant branchfrom the aorta.

For the purposes of general illustration, and with reference to FIG. 1,a simple schematic representation of a section of brain vascular anatomyis shown. As shown in FIG. 1, the ophthalmic segment of the carotidartery OA is shown having a tortuous segment 5. Distal to the ophthalmicartery is the intracranial internal carotid artery IICA, the anteriorcerebral artery ACA, the M1 segment of the middle cerebral artery andthe M2 segment of the middle cerebral artery. A blood clot or occlusionY is shown within the M1 segment.

Usually, when the physician has entered the carotid artery with thecatheter, the intracranial occlusion is confirmed by injecting a bolusof xray dye into the patient and taking xray pictures that then assistthe physician in accurately determining the location and size of theocclusion in order that the microwire and microcatheter are advanced tothe desired position relative to the occlusion.

At this stage, when a microwire has been advanced to the clot, there arevarying technologies and techniques that can be used to recanalize theblood vessel.

The most commonly used technology uses a self-expanding stent or stentretriever as a means to withdraw the thrombus responsible for theocclusion. In this procedure, a microcatheter with the help of themicrowire is advanced beyond the clot using xray guidance. A guidecatheter having a balloon will typically also be advanced to a positionin the internal carotid artery in the neck. Subsequently, theself-expanding stent is advanced into the microcatheter and is gentlydeployed across the occlusion by withdrawing the microcatheter andunsheathing the stent. Usually after deployment of the stentriever thereis some degree of forward flow. After waiting for a few minutes thethrombus gets entangled in the tines of the stent retriever. At thisstage, the balloon in the guide catheter is inflated to preventantegrade (forward) flow in the vessels, and the stent is withdrawnwhile applying suction (reversal of flow direction) at the guidecatheter in the neck. The clot is thereafter removed through the guidecatheter.

This approach has a few disadvantages including that the procedure doesnot always work for various reasons. For example, depending on theanatomy of the patient, applying suction pressure at the neck sometimesdoes not get transmitted to the clot particularly if there are otherbranches (from a patent circle of Willis) that may provide blood flow ina way that the suction pressure is not transmitted to the occludedvessel. In addition, there is also a potential for the clot to fragmentand move into distal vessels. Further still, managing and placingballoon guide catheters can be technically challenging and potentiallytime consuming. In addition, self-expanding stents are expensive.

As a result, there is a move towards making catheters with a largerinner lumen that are flexible enough that they can be advanced into thebrain vessels (typically the middle cerebral artery) and into a positionsuch that the catheter can be used to directly suck the clot through thecatheter rather than using an expandable stent. This procedure overcomessome of the disadvantages including applying suction pressure directlyto the clot in a manner that is not dependent on the patient's anatomy.In addition, the costs will be lower if a stent is not used and thisprocedure may also save time. Local suction may also reduce thelikelihood of clot fragmentation.

However there are significant limitations to the current generation oflarge bore distal access catheters (DACs). One of these is the abilityof these catheters to move through those blood vessels having asignificant curvature. In particular, it is known that most strokesoccur in older people where the tortuousity of certain blood vessels maybe greater than the same blood vessels of a younger person due toage-related changes in the vasculature. Also, the inner surface of thevessels in an older person may not be as smooth because ofatherosclerotic disease. Importantly, both of these conditions cancompound the problem of moving catheters through the vasculature of astroke patient.

As shown in FIGS. 2 and 2A, the procedure of inserting a large boredistal access catheter 18 typically involves the manipulation of atri-axial system comprising a microwire 12 a inside a microcatheter 12 binside a distal access catheter (DAC) 18 through the vasculature.Initially, the microwire and microcatheter are placed in the carotidartery in the neck and are then advanced to beyond the clot. Using themicrowire and microcatheter as support, the distal access catheter isthen advanced forward to the desired position adjacent the clot. Incertain locations, this procedure does not often work properly as thedistal access catheter gets stuck around tight bends especially in theophthalmic bend of the internal carotid artery as shown in FIG. 2A. Thatis, the outer edge 18 a of the DAC may be pushed into the outer surfaceof the ophthalmic bend which often leads to it becoming stuck. Thisproblem is compounded by the difference in diameter of the distal end ofthe DAC relative to the diameter of the microcatheter 12 b that createsa gap 17. If the DAC gets stuck, this results in delays.

One solution that has been proposed to address this problem of the DACgetting stuck is to deploy the stentriever through the microcatheter anduse the friction of the stentriever against the vessel and clot asleverage to be able to manipulate the distal access catheter through thebend. That is, by a combination of gently pushing and pulling thestentriever and DAC, the DAC can be advanced around the tight curvatureof the ophthalmic bend. While this can be successful, this isdisadvantaged by the significant cost increase of using a stent and itcan also be time consuming. Moreover, given the differences in sizebetween the DAC and microcatheter, the gap 17 may prevent forwardmovement of the DAC over the microcatheter as the distal end of the DACcannot be bent enough within the tight curve.

Accordingly, there has been a need for a system that in particular aidsthe movement of a larger bore catheter (i.e. a distal access catheter)through the vasculature and particularly regions of the vasculaturehaving a high tortuousity.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a system forintracranial access through a patient's vasculature to access anintracranial occlusion, the system including a variable diameter guideand support system for steering and advancing a flexible line ofmaterial through the patient's vasculature, the variable guide andsupport system having a distal tip region and an expanded sectionwherein the expanded section has a distal tapering surface connectingthe distal tip region to the expanded section and wherein the expandedsection proximal to the distal tapering surface has a cylindricalsurface having an outer diameter greater than the diameter of the distaltip region.

In another embodiment, the variable diameter guide and support systemincludes a proximal support section having a flexible line of materialhaving a diameter less than the cylindrical surface and a strengthsufficient to advance the inner guide and support system through thepatient's vasculature.

In another embodiment, a distal access catheter is operatively connectedto the variable diameter guide and support system and wherein the distalaccess catheter has a distal inner diameter substantially correspondingto the diameter of the cylindrical surface and wherein the distal accesscatheter can move coaxially relative to the cylindrical surface.

In various embodiments, the cylindrical surface has an axial length of6-10 cm and/or the distal tapering surface has an axial length of 4-6 cmand/or the diameter of the cylindrical surface is about 0.058-0.075inches and/or the diameter of the distal tip section is about0.014-0.016 inches and/or the proximal support section has a diameter ofabout 0.035 inches.

In one embodiment, the distal tip section and proximal support sectionare connected together and the expanded section is independently andcoaxially moveable with respect to the distal tip section and proximalsupport section.

In yet another embodiment, the distal access catheter has an outerdiameter of 0.065-0.075 inches.

In a further embodiment, the expanded section has a flexibility enablingmovement through a vessel having a 1-1.5 cm diameter.

In another aspect, the invention provides a method of accessing anintracranial occlusion through a patient's vasculature comprising thestep of: a) advancing an inner guide and support system through thepatient's vasculature, the inner guide and support system having adistal tip region and an expanded section wherein the expanded sectionhas a distal tapering surface connecting the distal tip region to theexpanded section and wherein the expanded section proximal to the distaltapering surface has a cylindrical surface having an outer diametergreater than the diameter of the distal tip region; and wherein theinner guide and support system is operatively connected to a distalaccess catheter having a distal inner diameter substantiallycorresponding to the diameter of the cylindrical surface and wherein thedistal access catheter can move coaxially relative to the cylindricalsurface and b) manipulating the inner guide and support system anddistal access catheter through the patient's vasculature by acombination of torsional movements of the inner guide and support systemand coaxial movements of the inner guide and support system relative tothe distal access catheter to move the distal access catheter throughregions of the patient's vasculature having a high tortuosity.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features and advantages of the invention will beapparent from the following description of particular embodiments of theinvention, as illustrated in the accompanying drawings. The drawings arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of various embodiments of the invention.Similar reference numerals indicate similar components.

FIG. 1 is a schematic view of brain vascular anatomy showing theophthalmic artery (OA), intracranial internal carotid artery (IICA),anterior cerebral artery (ACA), M1 segment of the middle cerebral arteryand M2 segment of the middle cerebral artery.

FIG. 2 is a view of a typical microwire, microcatheter and distal accesscatheter that may used for recanalization procedures in accordance withthe prior art.

FIG. 2A is a view of the ophthalmic bend illustrating the problem ofadvancing a DAC over a microcatheter in a region of high tortuosity.

FIG. 3 is a view of an intracranial access system (IAS) in accordancewith one embodiment of the invention.

FIGS. 3A, 3B, 3C and 3D are side views of an assembled IAS (3A), distalaccess catheter (3B), expanded section (3C) and microwire (3D) inaccordance with one embodiment of the invention.

FIG. 4 is a view of a multisegment coaxial wire having an expandedsection in accordance with one embodiment of the invention, where aninner core is moveable within the outer part of the wire. This outerpart may be a highly flexible wire or a variable diameter catheter.

DETAILED DESCRIPTION OF THE INVENTION

Various aspects of the invention will now be described with reference tothe figures. For the purposes of illustration, components depicted inthe figures are not necessarily drawn to scale. Instead, emphasis isplaced on highlighting the various contributions of the components tothe functionality of various aspects of the invention. A number ofpossible alternative features are introduced during the course of thisdescription. It is to be understood that, according to the knowledge andjudgment of persons skilled in the art, such alternative features may besubstituted in various combinations to arrive at different embodimentsof the present invention.

In particular, intracranial access systems (IAS) 10 that can facilitatethe movement of a larger diameter catheter through sections of apatient's vasculature having a high curvature are described.

In a first embodiment, as shown in FIG. 3, the intracranial accesssystem 10 comprises a distal tip section 12, an expanded section 14 anda proximal support section 16. The IAS may include a distal accesscatheter 18. As described in greater detail below, a middle portion ofthe IAS 14 b is of a diameter that fits into and supports a distal end18 a of the DAC. The IAS will typically have a total length of about 2m.

Distal Tip Section 12

The distal tip section 12 is generally a thin wire having a pre-formedor formable tip 12 d enabling intracranial access. The wire will have anappropriate atraumatic coating 12 e for intracranial use and willtypically have an outer diameter A of 0.014-0.016 inch. The length B ofdistal tip section will be in range of 12-24 cm. The internal wire mayextend the entire length of IAS.

Expanded Section 14

The expanded section 14 provides a tapered transition from the narrowerdistal tip section 12 to the wider inner diameter C of a DAC 18. In thecontext of this description, a “taper” is generally referred to as achange in diameter from one section of the IAS to another. That is, ataper implies a narrowing of diameter from a thicker region or awidening of diameter from a narrower region to a thicker region. Thepurpose of the expanded section is to prevent separation of the distaledge 18 a of the DAC from the narrower distal tip section 12 as thedistal region is being advanced and particularly as the distal regionand DAC are being moved through areas of high vascular curvature.

As shown, the expanded section 14 includes a distal tapered section 14a, a cylindrical central section 14 b and a proximal tapered section 14c. The central section 14 b will have an outer diameter D generallycorresponding to the inner diameter C of the distal end of the DAC. Asshown, the DAC may also include a DAC tapered section 18 b thattransitions the DAC from a narrower distal diameter C to a widerproximal diameter F.

Importantly, the IAS (namely the distal tip, expanded and proximalsupport sections) and DAC can move independently of each other. The IASis steerable. It would be expected that a skilled operator would advancethe IAS first and subsequently advance the DAC over the IAS. Theconfiguration would be maintained in a way that generally the distal endof the DAC would remain fixed in relation to expanded section 14 of theIAS to allow for smooth transition.

As can be seen, the central section 14 has a length G sufficiently longto enable this coaxial movement without causing the separation of theexpanded section 14 from the distal inner diameter C of the DAC. Inpractice, the central section with have a length G of approximately 8cm. The total length of the expanded section 14 between the distal tipsection 12 and proximal support section 16 will be about 12-15 cm. Thus,each of the tapered sections 14 a and 14 c will be about 2-4 cm long.

The outer diameter D of the central section 14 b will be approximately0.058 inches and will be capable of moving through a curve having a1-1.5 cm diameter. The central section 14 b is sufficiently strong inthe radial direction while being bent to prevent separation of the DACdistal end 18 a from the expanded section while moving around a tightcurve. The central portion may have additional coating such as ahydrophilic coating to reduce friction.

The central section 14 b and tapers may be a spiral wire and/or aplastic/rubber section having sufficient flexibility to enable bendingand movement through a tight curve and sufficient radial strength toprevent separation as described above. In the case of a spiral wire, thecentral section may be formed from the same wire as the distal tipsection or be a separate wire co-axially wound on an inner wire. In thecase of a plastic/rubber section, the central section may be cast on aninner wire. In some embodiments, the central section and taper may be acombination of both coaxially wound wire and cast plastic/rubber.

Proximal Support Section 16

The proximal support section 16 will typically have an outer diameter Hof about 0.035 inches and have sufficient axial compressive strengthenable the distal tip section 12 to be pushed forward and sufficienttorsional strength for turning of the distal tip section 12.

As shown in FIG. 4, in an alternate embodiment, the distal tip region 12and proximal support region 16 can be additionally coaxially movedrelative to the expanded section 14. Thus, in this embodiment, theexpanded region 14 forms a cover over the proximal support region havinga tapered region proximal support section 14 e that extends proximallyand that enables the physician to independently slide these separatecomponents relative to one another. In this embodiment expanded section14 may be made of metal or polymers or a combination (using technologiesused in making wires and microcatheters and DACs). As in the embodimentillustrated by FIG. 3, in this alternate embodiment, a DAC may bepreloaded onto the inner components.

Further, the underlying wire 12 a can be exchangeable so that if needed,once the distal access catheter is in place, the outer thicker part ofthe wire 12 a can be removed and the underlying thinner wire could stillbe used for stentriever purposes if needed.

FIG. 3A shows an assembly of an IAS with FIGS. 3B, 3C and 3D showing anouter DAC 18, expanded section 14 and inner wire 12 a.

Methods of Use

As described above, the IAS may be used to access an intracranialocclusion through a patient's vasculature. Generally, after the surgeonhas gained access to the patient's vasculature, the following generalsteps are followed:

-   -   a. advancing an inner guide and support system having a distal        tip region and an expanded section wherein the expanded section        has a distal tapering surface connecting the distal tip region        to the expanded section and wherein the expanded section        proximal to the distal tapering surface has a cylindrical        surface having an outer diameter greater than the diameter of        the distal tip region through the patient's vasculature together        with a distal access catheter having a distal inner diameter        substantially corresponding to the diameter of the cylindrical        surface and wherein the distal access catheter can move        coaxially relative to the cylindrical surface.    -   b. manipulating the inner guide and support system and distal        access catheter through the patient's vasculature by a        combination of torsional movements of the inner guide and        support system and coaxial movements of the inner guide and        support system relative to the distal access catheter to move        the distal access catheter through regions of the patient's        vasculature having a high tortuosity.

IAS Advantages

Noted advantages of this solution are:

-   -   a. As noted, if the IAS is preloaded into the distal access        catheter, preparation time for surgery will be reduced.    -   b. The system precludes the need for using a microcatheter or        microwire thus saving money.    -   c. If the clot can be successfully removed just by sucking        through the distal access catheter, it would obviate the need        for an expensive stent retriever.    -   d. The IAS system overcomes the current problem of distal access        catheters getting caught in tortuous curves especially in older        patients with atherosclerotic vessels.

Units of measure used in this specification are consistent with theunits used in the field of endovascular surgery. That is, both imperialand metric units are used where lengths are typically expressed inmetric units while diameters are expressed in imperial units.

Although the present invention has been described and illustrated withrespect to preferred embodiments and preferred uses thereof, it is notto be so limited since modifications and changes can be made thereinwhich are within the full, intended scope of the invention as understoodby those skilled in the art.

1. A system for intracranial access through a patient's vasculature toaccess an intracranial occlusion, the system comprising: a variablediameter guide and support system for steering and advancing a flexibleline of material through the patient's vasculature, the variable guideand support system having a distal tip region and an expanded sectionwherein the expanded section has a distal tapering surface connectingthe distal tip region to the expanded section and wherein the expandedsection proximal to the distal tapering surface has a cylindricalsurface having an outer diameter greater than the diameter of the distaltip region.
 2. The system as in claim 1, wherein the inner guide andsupport system further comprises a proximal support section having aflexible line of material having a diameter less than the cylindricalsurface and a strength sufficient to advance the inner guide and supportsystem through the patient's vasculature.
 3. The system as in claim 1,further comprising a distal access catheter operatively connected to theinner guide and support system and wherein the distal access catheterhas a distal inner diameter substantially corresponding to the diameterof the cylindrical surface and wherein the distal access catheter canmove coaxially relative to the cylindrical surface.
 4. The system as inclaim 3, wherein the cylindrical surface has an axial length of 6-10 cm.5. The system as in claim 3, wherein the distal tapering surface has anaxial length of 4-6 cm.
 6. The system as in claim 1, wherein thediameter of cylindrical surface is about 0.058-0.075 inches.
 7. Thesystem as in claim 1, wherein the diameter of the distal tip section isabout 0.014-0.016 inches.
 8. The system as in claim 2, wherein theproximal support section has a diameter of about 0.035 inches.
 9. Thesystem as in claim 2, wherein the distal tip section and proximalsupport section are connected together and the expanded section isindependently and coaxially moveable with respect to the distal tipsection and proximal support section.
 10. The system as in claim 3,wherein the distal access catheter has an outer diameter of 0.065-0.075inches.
 11. The system as in claim 1, wherein the expanded section has aflexibility enabling movement through a vessel having a 1-1.5 cmdiameter.
 12. A method of accessing an intracranial occlusion through apatient's vasculature comprising the step of: advancing an inner guideand support system through the patient's vasculature, the inner guideand support system having a distal tip region and an expanded sectionwherein the expanded section has a distal tapering surface connectingthe distal tip region to the expanded section and wherein the expandedsection proximal to the distal tapering surface has a cylindricalsurface having an outer diameter greater than the diameter of the distaltip region, wherein the inner guide and support system is operativelyconnected to a distal access catheter having a distal inner diametersubstantially corresponding to the diameter of the cylindrical surfaceand wherein the distal access catheter can move coaxially relative tothe cylindrical surface; and manipulating the inner guide and supportsystem and distal access catheter through the patient's vasculature by acombination of torsional movements of the inner guide and support systemand coaxial movements of the inner guide and support system relative tothe distal access catheter to move the distal access catheter throughregions of the patient's vasculature having a high tortuosity.